Yeah I would be careful about anything that has a switch to automatically crush the can. I can just immagine someone putting the can in it and having their hand crushed
. I would use a button personally. If you are supposed to make it automated then make it so you have to close a little door around the can, then as soon as the door is closed it crushes it. This way you can say it is automated, and at the same time it has cool safety features.